People suffering from various forms of diabetes routinely need to test their blood to determine the level of blood glucose. The results of such tests can be used to determine what, if any, insulin or other medication needs to be administered. In one type of blood glucose testing system, biosensors are used to test a sample of blood.
Such a biosensor may have a generally flat, rectangular shape with a front or testing end and a rear or terminal end. The biosensor contains multiple electrodes near its testing end, each of which electrically links to a corresponding lead at a terminal end of the biosensor. On the electrodes, there is at least one layer of reagent consisting of enzyme, mediator and certain inactive ingredients. The reagent will enzymatically react with blood glucose and produce redox current at the electrodes. The testing end of the biosensor is adapted to receive the fluid being tested, for example, blood that has accumulated on a person's finger after the finger has been pricked. The fluid is drawn into a capillary channel that extends in the biosensor from the tip of the testing end to the reagent/electrodes by capillary action so that a sufficient amount of fluid to be tested is drawn into the biosensor. The fluid then reacts with the reagent in the biosensor with the result that an electrical signal indicative of the blood glucose level in the blood being tested is supplied from the electrodes to their corresponding leads located at the rear or terminal end of the biosensor.
In such biosensors, multiple electrodes, and hence, multiple leads are used. When a biosensor is inserted into its associated meter and is positioned into the testing position, such leads are connected to the meter electronic circuitry via a connector in the meter. If the biosensor is already in the meter, then it is positioned in the testing position. The connector, in general, has the same number of contacts as the leads on the biosensor (although in some applications, there can be more contacts or more leads). Each lead is connected to an individual connector contact, which in turn is connected to the meter circuitry. However, connection errors, such as a short or open, could occur. A short condition occurs, if, not by design, two connector contacts touch the same lead or one of the contacts touches more than one lead. An open condition occurs if, not by design, a contact does not touch any lead. Such short and open conditions could cause an erroneous reading, which could result in harmful consequences. Such faulty meter-sensor connections may be caused by damaged contacts in the connector or defective leads on the biosensor. Therefore, it is crucial for such a meter to self-detect the meter-sensor connection errors such as a short condition or an open condition.